SB 210396 is an active and selective primatized monoclonal antibody directed at a CD4 antigenic determinant of a known structure. This compound has already demonstrated safety in patients with rheumatoid arthritis at doses from .03 to 4.0 mg/kg. Clinical activity was observed with single doses of .12 to 1 mg/kg. By transiently decreasing the number and activity of CD4 positive lymphocytes, SB 210396 may improve the clinical outcomes in asthma via a reduction in the inflammatory events.